    <td class='h23 m00'></td>
    <td class='h23 m30'></td>")
 
-(defn- add-new-row-to-timetable-day
+(defn- add-new-row-to-timetable-day!
   "Adds a new row to the 0-indexed day in the Timetable, where 0 = Monday,
    1 = Tuesday, until 4 = Friday."
   [day]

        (get-css-hour-minute-classes-for-time startTime)]
    ; Create new row if necessary
    (if (= rowNum (get-nr-rows-in-timetable-day day))
        (add-new-row-to-timetable-day day))

    ; Update in-memory representation of timetable
    (timetable-add-lesson day

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(defn- add-missing-td-elements-replacing-lesson
  "Adds <td> elements that were removed by the `add-module-lesson!` function
   to make way for the lesson."
  [$parentTd ttLessonInfo]
  (let [startTime (:startTime ttLessonInfo)
